| 摘要 |
A process for the manufacture of a salt mixture of Na, Mg and optionally Ca orthophosphates wherein H3PO4, NaOH solution and/or Na phosphate solutions or mixtures of Na orthophosphate and H3PO4, and MgO, optionally in admixture with CaO are reacted with sustained agitation and mixing for a period of 10-45 minutes. The H3PO4 contains 45-60 weight per cent P2O5 and the MgO and the CaO have a grain size < 0.5 mm.-The bulk of adhering water is evaporated by the heat of neutralization and the resulting mixture is dried and optionally comminuted so as to remove residual adhering water. The reaction may be carried out at 80-120 DEG C.-The residual adhering water may be removed by mill-drying. The salt mixture may have a water content of 35 weight per cent and be mixed with recycled material from the mill-drying stage to reduce the water content before mill-drying the mixture. Calcined dolomite may be used initially. H3PO4 partially neutralized with NaOH and/or Na2CO3 may be used initially, e.g. a mixture of Na2O and P2O5 in the ratio 1 : 2 to 3. The starting materials may pass through a mixing range, e.g. liquid materials fed near the opening and solid materials being fed at a place immediately thereafter. The product has a pH of 6 to 8 in aqueous solution, and the salt mixture may contain Na2HPO4 with and without water of crystallization MgHPO4.3H2O and the calcium if present in the form CaHPO4.2H2O or CaHPO4. The composition of the product may vary within the limits 35-50 weight per cent P2O5, 10-20 weight per cent Na2O, 4-22 weight per cent MgO and 0-18 weight per cent CaO and a proportion of water escaping on calcining at 800 DEG C. of 6-23 weight per cent. The mixer may be a double shaft self-mixing mixer and be connected to a wind-sifter to recycle oversize material. Centrifugal mixers may supply the continuous mixer. The mixer paddles may be partially set to counter-transport position and weirs may be provided for accumulating product.ALSO:A salt mixture of sodium, magnesium and optionally calcium orthophosphates is used as an animal food additive. |
